Which of the equations correctly describes incomplete combustion? (A) C₂H₅OH(l) + 2O₂(g) → 2CO(g) + 3H₂O(l) (B) C₂H₅OH(l) + rac{3}{2}O₂(g) → 2CO₂(g) + 3H₂O(l) (C) C₂H₅OH(l) + 3O₂(g) → 2CO₂(g) + 3H₂O(l) (D) C₂H₅OH(l) + 2O₂(g) → C(s) + CO(g) + 3H₂O(l) - HSC - SSCE Chemistry - Question 10 - 2015 - Paper 1

Incomplete combustion occurs when there isn't enough oxygen to completely convert the fuel (in this case, ethanol - C₂H₅OH) to carbon dioxide and water.

Analyzing each option:

• Option (A): C₂H₅OH(l) + 2O₂(g) → 2CO(g) + 3H₂O(l)

  • This suggests that ethanol is producing carbon monoxide (CO) instead of carbon dioxide (CO₂), indicating incomplete combustion.

• Option (B): C₂H₅OH(l) + \frac{3}{2}O₂(g) → 2CO₂(g) + 3H₂O(l)

  • This reaction shows complete combustion with all products being carbon dioxide and water.

• Option (C): C₂H₅OH(l) + 3O₂(g) → 2CO₂(g) + 3H₂O(l)

  • Again, this is a representation of complete combustion.

• Option (D): C₂H₅OH(l) + 2O₂(g) → C(s) + CO(g) + 3H₂O(l)

  • This option indicates that solid carbon (C) is a product, confirming incomplete combustion as some carbon is not oxidized to CO₂.

Thus, the correct equations describing incomplete combustion are (A) and (D).